The use of centrifugal spinning apparatus for the production of a variety of product forms such as fibers, particles and powders and as a reactor for chemical reactions is known. Examples of such uses and apparatus therefore can be found in GB-A-1439777, GB-A-1515511, GB-A-2004204, GB-A-2004206, GB-A-2026904, GB-A-2118866, EP-B-0017510, EP-B-0056001, EP-A-0168817, EP-A-0177207, U.S. Pat. No. 4,178,336, U.S. Pat. No. 4,197,063, U.S. Pat. No. 4,440,700 and U.S. Pat. No. 4,678,490. The spinning conditions can be controlled to determine whether liquid medium being spun forms fibres or filaments or breaks up into droplets to form particles and powders.
Typically, the apparatus has a disc or annular member to which liquid medium, ie solution or melt, is fed to be spun therefrom. Discs tend to spin the liquid medium in sheet form which is not conducive to forming good fibres or relatively uniform powders. In apparatus utilising an annular member, the member may have a plurality of passages through which the liquid medium is spun. In use, the passages of such members may become blocked. Additionally, the liquid medium my creep circumferentially around the member away from the exit of the passage leading to intermittent break away of the medium from the surface of the member and deterioration of quality of the product. In alternative forms of annular member, the liquid medium may be spun from an end of the member. However, circumferential creep of the medium may be a problem in that instance also, as may be uniformity of flow of the liquid medium to the edge of the member from which it is spun. Other problems associated with the spinning of fibers include "shot" formation, ie small particles, fiber melding and fiber bonding, wide uncontrolled variations in particle/fibre sizes and malformations such as lumps of material.
It is an object of the present invention to provide a centrifugal spinning apparatus in which one or more of the aforementioned disadvantages is reduced or obviated.